SunSPoT – an online solar power calculator

by Tiffany Paczek
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SunSPoT, a new online platform that can be used to calculate the solar power potential of any rooftop – home, business, factory or school – launched in Sydney on Thursday 5 April 2018.

The online tool has already discovered enormous untapped potential for solar power installations across a range of buildings in Adelaide, Brisbane, Canberra, Melbourne, Perth and Sydney, with more cities and towns to be added as the programs expands.

About the calculations

SunSPoT uses 3D building and vegetation models from AAM and Typical Meteorological Year (TMY) weather data from the US Department of Energy Simulation Software Weather Data webpage to calculate average annual and monthly incident solar radiation on a building surface and the expected performance of a typical PV system of the size specified by the user, with PV panel orientation and tilt defaulting to that of the roof surface, or defined by the user.

Solar radiation (insolation) heat map layer

An insolation heat map displaying the average level of solar radiation (insolation) in kWh/m2/day. This layer can be used to quickly visualise the solar potential of different building surfaces. Surfaces highlighted in red provide the best options for solar. A key to the insolation heat map is shown beside the insolation slider.

Identify the specific roof area for investigation

After using the data layers to visualise your building’s solar potential, you can draw a shape over an area of interest on a single roof surface, and then simulate the annual PV output that would be expected over that area.

Review the results for your identified area

After drawing your area of interest, the results panel will appear on the right-hand side of the screen. The panel will by default display the results for a flush mounted PV system (which is mounted in parallel to the roof surface, with an air gap of approximately 10 cm between the PV panels and the roof). You can switch to a rack-mounted PV system at an alternative tilt and orientation.

The simulation results include:

  • Approximate area – the approximate area in square metres of the drawn polygon/rectangle.
  • Insolation – the average level of solar radiation (insolation in kWh/m2/day) available at the surface within the identified area.
  • Orientation – the average orientation of the surface within the identified area.
  • Tilt – the average tilt angle of the surface within the identified area.
  • System size: – the estimated photovoltaic (PV) system size in kW that can be installed on the surface within the identified area. System size will change when a new roof area is selected, which fits a different number of panel; and also when rack or flush mounting, or different tilt and orientation options are used on the same roof area, as the spacing between panels changes to avoid self shading.
  • AC power output – the estimated monthly and annual AC energy output in kWh of the PV system. This can be compared to the energy consumption in kWh of the building by reviewing the relevant electricity bills.
  • Annual output per kW of installed capacity – the estimated annual output from the PV system per KW of installed capacity in kWh/kW. This can be used to compare the performance of PV systems mounted at different locations or tilt/orientation angles.
  • Estimated annual saving – the estimated annual financial savings in dollars per annum, assuming the electricity price in the box. This is calculated by multiplying the kWh generated annually by the electricity price in c/kWh. You can adjust the electricity price in order to assess the value of electricity generated by the PV system when it is used to offset retail electricity prices, which are typically 20-30 c/kWh for residential customers and 12-25 c/kWh for commercial customers in Australian cities. Alternatively, you may enter the price that a retailer might offer for PV electricity exported at times when the PV generation exceeds the load. This may be from 0 to 60 c/kWh, depending on the retailer and the availability of premium feed-in tariffs.
  • CO2 offset – the estimated annual carbon emissions savings in tonnes of CO2 per annum, based on the average emissions from grid electricity in the relevant state or territory, and considering emissions created during the manufacture of the PV system.

Developed by the Australian Photovoltaics Institute and the University of New South Wales, and funded by the Australian government’s Smart Cities and Suburbs program, SunSPoT was launched by the Hon Paul Fletcher MP, Minister for Urban Infrastructure and Cities.

The SunSPoT online platform can be found at

Image: folewu ©

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